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A. BRQoKs ETAL 3,322,941

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FIN E -u L SYNCHRO C /0 /f s SDEEO {3 COAQSE C y MEOlOM ,srz-LECTOQ DETECTOR 7SELECTOR r 3 SDEED Fmr? f I COM-SE Acommel -s ffns FINE /3 /4 EL. I( Sl CTO@ ZERO MEMORY L FORCE, s SDEE D Y SAMDLING OSCILLATOD I `/o i la slQEEO 4 OA SE COMDLEMENTOQ MEDIUM CONTROL FINE l CONTROLS A A --"sM/IDLING o l CONTROL i f v* KAL FQEEZE AU A -v L DQOCRAMDULSE )7 OENEQATOQ j CLOCK l 2A SPEED Q 1 L \L 5C KC /7 May 3,0', `1967 I Filedreb. 24, 1964` A. BROOKS ETAL SYNCHRO To DIGITAL CONVERTOR 19 Sheets-Sheet l 9 FINE QEGISTEQ FINE CQQQECTGQ' LUMIN ESCENT DEAL'JOUTv LU MINESCENT DEADOUT United StateSPaterlt "ICC 3,322,941 SYNCHRO T0 DIGITAL CONVERTOR Alvin Brooks, Valley Cottage, Gerald Glatt, New York, Arthur Lehrer, Bayside, and Gordon Silverman, Jackson Heights, N.Y., assignors to Loral Electronics Corporation, New York, N.Y., a corporation of New York Filed Feb. 24, 1964, Ser. No. 346,682 2 Claims. (Cl. 23S- 154) This invention relates generally to lthe eld of electronic computers, of a type employed for converting analogue information supplied by driven synch-ros to digital form.

In most digital mechanisms, input information is presented in the form of -a digital number, usually represented as a group of Wires, with one ofthe discrete levels on each Wire. Since most synchros produce a continuous output, it is necessary to convert this output into the proper digital form so Ithat the resultant function will be compatible with -a digital device. The present disclosure relates to a device which will laccept electrical information from a synchro transmitter, synchro differential transmitter, or other similar device, and conve-rt this information into .a binary coded decimal output. It is' simpler in construction than are prior art devices based on similar principles.

IIt is among the principal objects of the present invention to provide an improved synchro to digi-ta-l convertor of the class described which employs a unique means for determining the exact shaft position of transmitters in multiple speed systems Where misalignment between the various transmitter components would ordinarily produce large errors.

Another object of the invention lies in the provision of a device of .the class described which will display the transmitter shaft transmission directly in engineering units representatives of the transmitter function, such as degrees, -or yards, including mixed functions, such as degrees and minutes.

Another object of the invention lies in the provision of means for the encoding of multiple speed functions, with la different speed for each function, and in which the different functions may represent different systems of units.

A further object of the invention lies in the provision of means for the encoding of multiple speed functions where, within a multiple speed system, the units may represent la system of units in which mixed ratios which are not units of ten may be employed.

Yet another objectl of the invention lies in the provision of means for the encoding and display of multiple speed transmissions directly into engineering units, rather than othe-r systems such as binary systems where considerable computation is subsequently necessary to convert the systems to .an equivalen-t engineering unit.

A further object of t-he invention lies in the provisionof means for eliminating the possibility lof lgross machine errors in the determination of .the attenuation points, so as to effectively cancel the effect of these errors.

i Still another object of the present invention lies in the provision of an improved synchroy to digital convertor in which the electronic components have been reduced to a basic minimum consistent with functions performed.

These objects, as well as other incidental ends and advantages, will more fully .appearv in the progress of the following disclosu-re, and be pointed out in the appended claims.

yBefore entering into a detailed consideration of the structural aspects of the disclosed embodiment, the following discussion is believed apposite.

l A method generally used .to convert an analogue voltage into a digital quantity is that of sequential comparison of the decoded digital quantity and the original analogue signal. Consider the following example, where all voltn 3,322,941 Patented May 30, 1967 ages from zero to sixteen volts are to be encodedvto the nearest volt. In essence, this encoding program can be accompli-shed by comparing the input voltage signal against a lr6-volt reference scale located in the encoder. To minimize the time required to do this, a comparison, at iirst, of half the refe-rence scale is made against the input scale. (For purposes of this example, assume the input quantity to be nine volts.) On any comparison, if the input signal is greater than lor equal to t-he reference signal, a bistable element will be set to a one state in order to remember this. Since half the yreference scale is less than nine volts, the first bistable element is set to one. Next, the input is compared against 3/4 of the reference scale (twelve volts). This time, Ithe result of the comparison is that the reference is greater than the input. Hence, the second bistable element Iremains zero, and the input is next compared to '1/2 plus 1/s, or 1%6, of the reference. Again the result leaves the bistable elements set at zero. The succeeding comparison is against 1/2 plus 3/16, or $56, of the reference scale, and since the. input is equal t-o 0&6 of the reference, the fourth bistable element is set to one. No further comparisons are necessary, since 5%[6 of the scale represents 9/16 of sixteen volts, or nine volts, and -it is only necessary to encode to the nearest volt measurement. The result of this sequential comparison is stored in the set -of bistable elements, as 1001. This is binary 9, which is `the digital representation of the 9-volt input that was to be encoded. To generalize the above example for any quantity, rst sequentially a number of bistable elements are set; then decoded (or the digital representation is converted to an equivalent analogue quantity); and compared to the input. The comparison reference is /ziti-/sil/wi i/zn, (n) depending upon the extent to which the input must be resolved, Where each sign depends on the result of the previous comparison. If the output is greater than the input, then the next sign is minus. lf the comparison indicates that the output is less .thanor equal Ito the input, the subsequent sign is plus.

To illustrate how this technique is applied to the problem of a synchro transmitter, consider the stator output voltages as a function of .transmitter shaft position for every 60 increment from 0 to 360. Two of the stator outputs are of one polarity, while the third is of the opposite polarity. These six results are unique in that v.there are no increments in which the same two stators are of the same polarity. Consequently, the polarities of the stator outputs (as compared to the polarity of the synchro Irefer-ence signal) can be used to determine within which one of the six sectors from 0 to 360 the shaft is located. Fur-ther, Within each sector, the ratio of the stator voltage which starts at zero (for that sector) to the stator voltage which reaches 1 (for that sector) is a trigonometric function of the form where a is the incremental .angle with each sector of the synchro .transmitter shaft position. Using the sector information and the angle within the sector, the position of'the transmitter shaft may be encoded to any desired accuracy and resolution. The encoding process for the case of a synchro transmitter is accomplished in the same way as was illustrated in the previous example, with one exception. Instead of comparing the input against a reference scale directly, one of the two stators selected (for each 60 sector) is used as .the reference and the other stator is compared against this in accordance with their functional relationship.

In the present invention, it is contemplated to accommodatethe translation of range and bearing information `into usable form for digital computors, without loss of Ratio 

1. IN A SYNCHRO DIGITAL CONVERTER, INCLUDING A MULTISPEED SYNCHRO TRANSMITTER HAVING COARSE AND FINE SPEED SYNCHRO, TRANSMISSION GATES DISPOSED IN THE STATOR LEADS OF SAID TRANSMITTER, A PHASE DETECTOR CONNECTED TO EACH OF SAID STATOR LEADS, RATIO DECODING MEANS, SECTOR SELECTOR CIRCUITRY, AND MEANS FOR DIGITIZING THE OUTPUT OF SAID SECTOR SELECTOR CIRCUITRY AND SAID RATIO DECODING MEANS AS A MULTI-SPEED FUNCTION, SAID RATIO DECODING MEANS INCLUDING A PLURALITY OF RESISTIVE TAPS, EACH CORRESPONDING TO AN ATTENUATION POINT INDICATIVE OF INSTANTANEOUS ROTATIONAL POSITION OF SAID SYNCHRO TRANSMITTER, THE IMPROVEMENT COMPRISING MEANS FOR SELECTING ONE OF SAID TAPS BASED UPON THE DETECTION OF AMBIGUITY EXISTING BETWEEN SAID FINE AND COARSE SPEED SYNCHROS; SAID LAST-MENTIONED MEANS INCLUDING MEANS FOR EXAMINING THE POSITIONS OF THE COARSE SYNCHRO TO DETERMINE WHETHER IT HAS PASSED THROUGH AN INDEX DESIGNATING A SUBMULTIPLE CORRESPONDING TO A COMPLETE ROTATION OF SAID FINE SYNCHRO, MEANS FOR SUBSEQUENTLY EXAMINING THE POSITION OF THE FINE SYNCHRO TO DETERMINE WHETHER IT HAS PASSED THE INDEX INDICATING A COMPLETE ROTAION THEROF, AND MEANS FOR SELECTING A RESISTIVE TAP CORRESPONDING TO THE POSITION OF SAID FINE SYNCHRO. 